Pump system

Abstract

This pump system comprises a plurality of pump modules that are connected in series. Each of the pump modules includes: a pump; a suction pipe that is connected to a suction port of the pump; a discharge pipe that is connected to a discharge port of the pump: and a bypass pipe that bypasses the pump and allows the suction pipe and the discharge pipe to be linked with each other. A pump module that is disposed at the most downstream portion among the plurality of pump modules further includes a minimum flow pipe connected to a portion of the discharge pipe that is downstream from the connection portion with the bypass pipe.

Description

Pump system

[0001] The present disclosure relates to a pump system including a plurality of pumps.

[0002] Conventionally, a pump configured to rotate an impeller housed in a sealed pump casing and apply centrifugal force to a liquid sucked into the pump casing to discharge it is known. Patent Document 1 discloses this type of pump.

[0003] The pot-type centrifugal pump disclosed in Patent Document 1 has an impeller and an electric motor for driving the impeller housed in a pot. The pump sucks in LNG from a suction port provided on the side of the pot and discharges it from a discharge port provided on the upper part of the pot. A suction line for sending the LNG stored in the LNG tank to the pump is connected to the suction port. A high-pressure gas supply line, that is, a discharge line for sending the LNG to a high-pressure gas demand destination is connected to the discharge port. A flow meter, a vaporizer, and an on-off valve are provided in the high-pressure gas supply line. Also, a minimum flow line is connected to the high-pressure gas supply line downstream of the flow meter and upstream of the vaporizer. Even when the LNG is not supplied to the high-pressure gas demand destination, the pump continues to be driven, and a minimum amount of LNG is returned to the LNG tank through the minimum flow line. A vent line for discharging the vaporized gas inside the pot is connected to a vent port provided on the upper part of the pot.

[0004] Japanese Unexamined Patent Application Publication No. 2005-226750

[0005] When stepwise boosting a fluid, it is conceivable to connect a plurality of pumps in series. However, connecting a plurality of pumps results in a complicated configuration.

[0006] The present disclosure has been made in view of the above circumstances, and an object thereof is to simplify the configuration in a pump system including a plurality of pumps connected in series.

[0007] To solve the above problems, a pump system according to one aspect of the present disclosure comprises a plurality of pump modules connected in series, each of the plurality of pump modules includes a pump, a suction pipe connected to the suction port of the pump, a discharge pipe connected to the discharge port of the pump, and a bypass pipe having a bypass valve, which allows fluid to flow from the suction pipe to the discharge pipe while avoiding the pump, and the pump module located furthest downstream of the plurality of pump modules further comprises a minimum flow pipe connected to the portion of the discharge pipe downstream of the connection to the bypass pipe.

[0008] According to this disclosure, the configuration of a pump system comprising multiple pumps connected in series can be simplified.

[0009] Figure 1 is a block diagram showing a schematic configuration of a pump system according to one embodiment of the present disclosure. Figure 2 is a diagram showing a schematic configuration of a modified pump system.

[0010] Next, embodiments of the present disclosure will be described with reference to the drawings. Figure 1 is a block diagram showing a schematic configuration of a pump system 1 according to one embodiment of the present disclosure. The pump system 1 according to this embodiment is installed, for example, in a line that supplies low-temperature liquefied gas from a liquefied gas source 11 to a high-pressure gas demanding device 12, and pressurizes the liquefied gas and sends it to the high-pressure gas receiving side. Examples of liquefied gas sources include liquefied gas storage tanks. Examples of high-pressure gas demanding devices 12 include turbines and internal combustion engines. The pump system 1 may be installed in a line that supplies liquefied gas to a tank or demand site instead of the high-pressure gas demanding device 12.

[0011] As shown in Figure 1, a pump system 1 according to one embodiment of the present disclosure comprises a plurality of pump modules 2 connected in series. The pump system 1 shown in Figure 1 comprises three stages of pump modules 2, but the number of pump modules 2 is not limited to this embodiment and may be two or more.

[0012] 《Configuration of Pump Module 2》 The configurations of multiple pump modules 2 are substantially the same, and the configuration of one of the multiple pump modules 2 will be described in detail below. Pump module 2 comprises a suction pipe 3 connected to the suction port 22 of pump 21, a discharge pipe 4 connected to the discharge port 23 of pump 21, and a bypass pipe 5 that bypasses pump 21 and connects the suction pipe 3 and the discharge pipe 4. Note that pump module 2 represents a functionally grouped part, but it does not need to be assembled as a single unit.

[0013] Pump 21 is a centrifugal pump. The structure of pump 21 is not particularly limited. For example, pump 21 comprises a container 26 and a pump body 27 housed in the container 26. The pump body 27 comprises, for example, a casing, an impeller housed in the casing, and a motor that rotates the impeller and shaft. The container 26 of pump 21 surrounds the pump body 27 and has the function of maintaining the liquid level. The container 26 is provided with a suction port 22, a discharge port 23, and a vent port 24. Pump 21 pressurizes the fluid drawn in from the suction port 22 and discharges it from the discharge port 23.

[0014] The suction pipe 3 is connected to the suction port 22 of the container 26, and the fluid drawn in by the pump 21 flows through it. The suction pipe 3 is connected to the liquefied gas source 11, or to the discharge pipe 4 of the pump 21 located upstream. The suction pipe 3 is provided with a suction valve 31. The suction valve 31 opens and closes the flow path of the suction pipe 3, or adjusts the flow rate of the fluid flowing through the suction pipe 3.

[0015] The discharge pipe 4 is connected to the discharge port 23 of the container 26, and the fluid discharged from the pump 21 flows through it. The suction pipe 3 is connected to the suction pipe 3 of the high-pressure gas demand equipment 12, or to the pump 21 located downstream. A check valve 41 is provided in the discharge pipe 4. The check valve 41 prevents the backflow of fluid from the discharge pipe 4 to the pump 21. However, when the pump 21 is stopped, the check valve 41 allows a small flow rate of liquid backflow from the discharge pipe 4 to the pump 21. For example, the valve body of the check valve 41 has a hole, and backflow of fluid is permitted through this hole.

[0016] The bypass pipe 5 connects the suction pipe 3 and the discharge pipe 4 fluidly, bypassing the pump 21. The fluid flowing through the bypass pipe 5 flows from the suction pipe 3 to the discharge pipe 4 without passing through the pump 21. The bypass pipe 5 is provided with a bypass valve 51. The bypass valve 51 opens and closes the flow path of the bypass pipe 5, or adjusts the flow rate of the fluid flowing through the bypass pipe 5.

[0017] A vent pipe 6 is connected to the vent port 24 of the pump 21. Gas, mainly containing vaporized liquefied gas, accumulates in the upper part of the container 26. The gas inside the container 26 is discharged to the outside through the vent pipe 6. A vent valve 61 is provided on the vent pipe 6. The container 26 is equipped with a liquid level sensor 25 that detects the liquid level of the liquefied gas inside the container 26. In the container 26, the liquid level is controlled within a predetermined range by the gas inside the casing. Specifically, when the liquid level detected by the liquid level sensor 25 falls below a predetermined range, the vent valve 61 is opened until the liquid level recovers to the predetermined range, the gas inside the container 26 is discharged, and liquid flows into the container 26. Through this level control, the liquid level in the container 26 is maintained within a predetermined range.

[0018] In the pump system 1 according to this embodiment, a first pump module 2A, a second pump module 2B, and a third pump module 2C are connected in series. Specifically, the suction pipe 3 of the first pump module 2A is connected to a liquefied gas source 11, the discharge pipe 4 of the first pump module 2A is connected to the suction pipe 3 of the second pump module 2B, the discharge pipe 4 of the pump module 2 is connected to the suction pipe 3 of the third pump module 2C, and the discharge pipe 4 of the third pump module 2C is connected to a high-pressure gas demanding device 12.

[0019] Furthermore, the pump system 1 has the upstream end of the minimum flow pipe 15 connected to the downstream portion of the pump module 2 located furthest downstream, that is, the third pump module 2C in this embodiment. The minimum flow pipe 15 may be connected to the portion of the discharge pipe 4 of the third pump module 2C downstream from the connection to the bypass pipe 5, or it may be connected to the piping that connects the discharge pipe 4 of the third pump module 2C to the high-pressure gas demand equipment 12. The downstream end of the minimum flow pipe 15 may be connected to the liquefied gas source 11, or it may be connected to the liquefied gas demand destination.

[0020] The minimum flow pipe 15 is equipped with a minimum flow valve 16 controlled by the control device 7. The minimum flow valve 16 is a flow rate control valve. The pump system 1 is also equipped with a flow sensor 17 that detects the total flow rate of the fluid flowing through the pump system 1. In the pump system 1 according to this embodiment, the flow sensor 17 is located downstream of the connection to the bypass pipe 5 and upstream of the connection to the minimum flow pipe 15 in the discharge pipe 4 of the third pump module 2C. The control device 7 adjusts the opening of the minimum flow valve 16 so that the flow rate of liquefied gas in the minimum flow pipe 15 is maintained at a minimum flow rate. When the pump system 1 is in operation and the flow rate of liquefied gas detected by the flow sensor 17 falls below a predetermined minimum flow rate, the control device 7 adjusts the opening of the minimum flow valve 16 so that the flow rate of liquefied gas detected by the flow sensor 17 is maintained at a minimum flow rate in the minimum flow pipe 15. The minimum flow rate is the minimum flow rate at which the pump 21 can operate stably and continuously without overheating, noise, or vibration. If the performance of the multiple pumps 21 in the pump system 1 differs, the largest value among the minimum flows of the multiple pumps 21 will be adopted as the minimum flow rate.

[0021] A relief pipe 18 may be provided in the minimum flow pipe 15. Both ends of the relief pipe 18 are connected to the minimum flow pipe 15, and the liquefied gas flowing into the minimum flow pipe 15 flows downstream of the minimum flow valve 16 by passing through the relief pipe 18, thus avoiding the minimum flow valve 16. The minimum flow pipe 15 is provided with an orifice 19 that limits the flow rate of the liquefied gas passing through the relief pipe 18. During operation of the pump system 1, a minimum flow of liquefied gas flows continuously through the relief pipe 18. Alternatively, instead of the relief pipe 18, the minimum opening of the minimum flow valve 16 may be limited to prevent it from being fully closed, thereby allowing fluid to flow through the minimum flow pipe 15.

[0022] 《Operation Method of Pump System 1》 The operation method of the pump system 1 with the above configuration will now be explained. In the pump system 1 during operation, all pumps 21 continue to operate regardless of the pressure of the liquefied gas supplied from the liquefied gas source 11 to the high-pressure gas demanding equipment 12. The pressure of the liquefied gas supplied to the high-pressure gas demanding equipment 12 may be adjusted by the number of pump modules 2 used and pump modules 2 that are stopped.

[0023] In the pump system 1 while it is shut down, all pump modules 2A, 2B, and 2C are in a standby state with the bypass valve 51 open, the suction valve 31 closed, and the pump 21 stopped.

[0024] In a shut-down pump system 1, if the temperature of pump 21 and its surroundings rises, the gas pressure of vaporized gas generated in the piping surrounding pump 21 may obstruct the discharge of pump 21, potentially causing pump 21 to stop due to insufficient minimum flow during pump startup. Furthermore, to enable quick startup of pump 21, it is useful to cool pump 21 and its surrounding piping while the pump system 1 is shut down. Therefore, in a shut-down pump system 1, a small amount of liquefied gas flows from the discharge pipe 4 into pump 21 through level control of pump 21, causing a small amount of liquefied gas to flow through pump 21 and discharge pipe 4, thus cooling pump 21 and discharge pipe 4. Additionally, in a shut-down pump system 1, a small amount of liquefied gas flows through the minimum flow pipe 15 via the relief pipe 18, cooling the minimum flow pipe 15.

[0025] When starting the pump system 1 from a stopped state, the starting operations are performed sequentially from the upstream pump modules 2A, 2B, and 2C. The starting operation of the pump system 1 includes a series of operations performed in the following order: closing the bypass valve 51, opening the suction valve 31, and starting the pump 21. Specifically, the starting operation is performed first in the first pump module 2A, during which time the fluid in the standby second pump module 2B and the third pump module 2C flows through the bypass pipe 5, avoiding the pump 21. This prevents the fluid from flowing into the pump 21 and causing the pump 21 to start up in the standby second pump module 2B and the third pump module 2C. Consequently, the occurrence of malfunctions in the pump 21 is suppressed. After the starting operation of the first pump module 2A is completed, the starting operation of the second pump module 2B is performed while the third pump module 2C remains in standby mode. After the starting operation of the second pump module 2B is completed, the starting operation of the third pump module 2C is performed last.

[0026] In the above configuration, the pump modules 2A, 2B, and 2C are started in order from the upstream modules. However, the pump modules 2A, 2B, and 2C may be started in order from the downstream modules. Alternatively, all pump modules 2A, 2B, and 2C may be started simultaneously. However, even if operation commands are issued to all pump modules 2A, 2B, and 2C simultaneously, it is difficult for all of them to operate synchronously due to individual differences, etc. Therefore, it is preferable to start the pump modules 2A, 2B, and 2C in order from the upstream or downstream modules.

[0027] When pump system 1 is started, in each pump module 2A, 2B, and 2C, the liquefied gas flowing into the suction pipe 3 flows into the pump 21 from the suction port 22, is pressurized, and then discharged from the discharge port 23 into the discharge pipe 4, and flows through the discharge pipe 4 to the downstream pump module 2 or piping. If there is a pump module 2 that is not in use, the pump module 2 that is not in use is put into a standby state and fluid flows through the bypass pipe 5.

[0028] When stopping the pump system 1 while it is in operation, the stopping operations are performed sequentially from the downstream pump modules 2A, 2B, and 2C. The stopping operation of the pump system 1 includes a series of operations performed in the following order: stopping the pump 21, closing the suction valve 31, and opening the bypass valve 51. Specifically, first, the stopping operation is performed on the third pump module 2C while the first pump module 2A and the second pump module 2B are still in operation. After the stopping operation of the third pump module 2C is completed, the stopping operation is then performed on the second pump module 2B while the first pump module 2A is still in operation. After the stopping operation of the second pump module 2B is completed, finally, the stopping operation of the first pump module 2A is performed. By performing the stopping operations sequentially from the downstream pump modules 2A, 2B, and 2C in this manner, the fluid flows to the bypass pipe 5, avoiding the stopped pump 21, thus preventing fluid from flowing into the stopped pump 21 and causing malfunctions in the pump 21.

[0029] In the above description, the stopping operations are performed sequentially starting from the downstream pump modules 2A, 2B, and 2C. However, the stopping operations may also be performed sequentially starting from the upstream pump modules 2A, 2B, and 2C. Alternatively, all pump modules 2A, 2B, and 2C may be stopped simultaneously. However, even if operation commands are issued simultaneously to all pump modules 2A, 2B, and 2C, it is difficult for all pump modules 2A, 2B, and 2C to operate synchronously due to individual differences, etc. Therefore, it is preferable that the stopping operations be performed sequentially starting from the upstream or downstream pump modules 2A, 2B, and 2C.

[0030] [Modified Version] Next, a modified version of the above embodiment will be described. Figure 2 is a block diagram showing the schematic configuration of the pump system 1 according to the modified version. In this description of the modified version, the same or similar components as in the above embodiment are denoted by the same reference numerals in the drawings, and their descriptions are omitted.

[0031] As shown in Figure 2, the modified pump system 1 comprises multiple pump modules 2 connected in series to form a single pump row 201, 202, and multiple pump rows 201, 202 connected in parallel. The configuration of the pump rows 201, 202 is substantially the same as that of the embodiment described above, and a detailed explanation is omitted.

[0032] In the modified pump system 1, the suction pipes 3 of the uppermost pump modules 2 of pump rows 201 and 202 are connected to each other, and the discharge pipes 4 of the lowermost pump modules 2 of pump rows 201 and 202 are connected to each other.

[0033] Thus, by providing multiple pump rows 201 and 202, the pump system 1 can increase or decrease the flow rate of liquefied gas delivered by the pump system 1.

[0034] [Summary] The pump system 1 according to the first item of this disclosure comprises a plurality of pump modules 2 connected in series, each of the plurality of pump modules 2 includes a pump 21, a suction pipe 3 connected to the suction port 22 of the pump 21, a discharge pipe 4 connected to the discharge port 23 of the pump 21, and a bypass pipe 5 that connects the suction pipe 3 and the discharge pipe 4 while avoiding the pump 21, and the pump module 2 located furthest downstream of the plurality of pump modules 2 further includes a minimum flow pipe 15 connected to the portion of the discharge pipe 4 downstream from the connection point of the bypass pipe 5.

[0035] Conventionally, each pump module is equipped with numerous pipes, such as suction pipes, discharge pipes, and minimum flow pipes, resulting in a very complex piping configuration when multiple pump modules are connected in series. In contrast, in the pump system 1 according to this disclosure, the minimum flow pipe 15 is provided only in the downstream pump module 2 among the multiple pump modules 2 connected in series. Therefore, the configuration can be simplified compared to a pump system 1 equipped with multiple pumps 21 connected in series, where each pump module 2 is equipped with a minimum flow pipe 15. Since pump systems that pressurize fluids with low liquid density, such as liquefied hydrogen, require multi-stage pumps, the pump system 1 according to this disclosure is particularly useful as a pump system 1 for pressurizing fluids with low liquid density.

[0036] The pump system 1 according to the second item of this disclosure is the pump system 1 according to the first item, wherein the pump module 2 located furthest downstream among the plurality of pump modules 2 includes a flow sensor 17 located downstream of the connection of the bypass pipe 5 of the discharge pipe 4 and upstream of the connection of the minimum flow pipe 15.

[0037] In the pump system 1 with the above configuration, the flow sensor 17 is provided only in the pump module 2 located furthest downstream among the multiple pump modules 2 connected in series. Therefore, the configuration can be simplified compared to a pump system 1 with multiple pumps 21 connected in series, where the flow sensor 17 is provided in each pump module 2.

[0038] The pump system 1 according to the third item of this disclosure is the pump system 1 according to the second item, wherein the minimum flow pipe 15 has a minimum flow valve 16 that opens when the fluid flow rate detected by the flow sensor 17 falls below a predetermined minimum flow rate.

[0039] In the pump system 1 with the above configuration, the minimum flow pipe 15 and minimum flow valve 16 are provided only in the downstream pump module 2 among the multiple pump modules 2 connected in series. Therefore, compared to the case where each pump module 2 is provided with a minimum flow pipe 15 in multiple directly connected pump modules 2, the number of minimum flow valves 16 can be reduced, and the configuration can be simplified.

[0040] The pump system 1 according to the fourth item of this disclosure is the pump system 1 according to the third item, and includes a control device 7 that operates a minimum flow valve 16 so that the flow in the minimum flow pipe 15 maintains a predetermined minimum flow based on the flow rate detected by the flow sensor 17.

[0041] In the pump system 1 with the above configuration, the minimum flow pipe 15 and minimum flow valve 16 are provided only in the downstream pump module 2 among the multiple pump modules 2 connected in series. This simplifies the configuration compared to the case where each pump module 2 is equipped with a control device 7.

[0042] The pump system 1 according to item 5 of this disclosure is the pump system 1 according to item 3 or 4, wherein the minimum flow pipe 15 has a relief pipe 18 through which the fluid flows, avoiding the minimum flow valve 16.

[0043] As a result, in the pump system 1 with the above configuration, the minimum flow pipe 15 and the relief pipe 18 are provided only in the downstream pump module 2 among the multiple pump modules 2 connected in series, thus simplifying the configuration compared to the case where each pump module 2 is provided with a relief pipe 18.

[0044] The pump system 1 according to the sixth item of the present disclosure is the pump system 1 according to any one of the first to fifth items, in which a plurality of pump modules 2 connected in series are taken as one pump row 201, 202, and a plurality of pump rows 201, 201 connected in parallel are provided.

[0045] In the pump system 1 configured as described above, the flow rate of the liquefied gas can be increased by increasing the pump rows 201, 202.

[0046] The functions realized by the control device 7 described in this specification may be implemented in circuitry or processing circuitry including a general-purpose processor, a specific-purpose processor, an integrated circuit, ASICs (Application Specific Integrated Circuits), a CPU (Central Processing Unit), a conventional circuit, and / or a combination thereof, programmed to realize the described functions. The processor includes transistors and other circuits and is regarded as circuitry or processing circuitry. The processor may be a programmed processor that executes a program stored in a memory. In this specification, circuitry, unit, and means are hardware programmed to realize the described functions or hardware that executes them. The hardware may be any hardware disclosed in this specification or any hardware known to be programmed or execute to realize the described functions. When the hardware is a processor regarded as a type of circuitry, the circuitry, means, or unit is a combination of hardware and software used to configure the hardware and / or the processor.

[0047] The embodiments described above are presented for illustrative and explanatory purposes only and are not intended to limit the disclosure to the forms disclosed herein. For example, in the detailed description above, various features of the disclosure are grouped into one embodiment for the purpose of streamlining the disclosure, but some of the features may be combined. Also, some of the features included in the disclosure may be combined into alternative embodiments, configurations, or aspects other than those discussed above.

[0048] 1: Pump system 2: Pump module 3: Suction pipe 4: Discharge pipe 5: Bypass pipe 7: Control device 15: Minimum flow pipe 16: Minimum flow valve 17: Flow sensor 18: Relief pipe 21: Pump 22: Suction port 23: Discharge port 51: Bypass valve 201, 202: Pump train

Claims

1. A pump system comprising a plurality of pump modules connected in series, each of the plurality of pump modules including a pump, a suction pipe connected to the suction port of the pump, a discharge pipe connected to the discharge port of the pump, and a bypass pipe that bypasses the pump and connects the suction pipe and the discharge pipe, wherein the pump module located furthest downstream of the plurality of pump modules further includes a minimum flow pipe connected to the portion of the discharge pipe downstream of the connection to the bypass pipe.

2. The pump system according to claim 1, wherein the pump module located furthest downstream of the plurality of pump modules includes a flow sensor located downstream of the connection of the bypass pipe to the discharge pipe and upstream of the connection of the minimum flow pipe.

3. The pump system according to claim 2, wherein the minimum flow pipe has a minimum flow valve that opens when the fluid flow rate detected by the flow sensor falls below a predetermined minimum flow rate.

4. The pump system according to claim 3, further comprising a control device that operates the minimum flow valve so that the flow in the minimum flow pipe maintains a predetermined minimum flow based on the flow rate detected by the flow sensor.

5. The pump system according to claim 3 or 4, wherein the minimum flow pipe has a relief pipe through which fluid flows, avoiding the minimum flow valve.

6. The pump system according to claim 1, comprising a plurality of pump modules connected in series to form a single pump row, and a plurality of such pump rows connected in parallel.

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